Part

 1 I|     tries a man just as muscular exertion does. But whatever of the
 2 I|         greater and more intense exertion of the muscles than that
 3 I|          the different degree of exertion of the muscles in human
 4 I|        machines. The greater the exertion, and the longer it lasts,
 5 I|         arm.~From the feeling of exertion and fatigue in our muscles,
 6 I| compelled to use a corresponding exertion in raising the weight?~The
 7 I|       moment they facilitate the exertion, also prolong it, so that
 8 I|       raise the load by the same exertion of force as each one of
 9 I|          without any appreciable exertion of the arm, may be set in
10 I|          without any appreciable exertion of force, to place it in
11 I|       sure only one-sixth of the exertion, which he would have to